1. Field
This disclosure relates generally to data processing, and more specifically, to a data processing system having temporally selective redundancy.
2. Related Art
Integrated circuit data processing systems used in safety-critical applications, such as those used in automotive anti-lock braking, generally require redundancy to detect soft (transient) and hard (permanent) failures. One redundancy technique, known as modular redundancy, provides two or more processors executing the same instructions in “lockstep”. The actions of two fully operational processors running in lockstep are identical. An error is indicated when the processor actions differ from each other. Running processors in lockstep to provide hardware redundancy is very expensive in both system cost and power consumption. It is also inflexible and effectively doubles the chances of failures occurring. Temporal redundancy is most commonly used to detect and correct soft errors. In general, temporal redundancy re-performs operations in the same form, or in an equivalent form, on the same hardware. Temporal redundancy has had limited success in detecting and correcting hard errors. Hard errors are more commonly detected by circuit redundancy in which operations may be performed, simultaneously or not, in separate circuitry.